It is well known that computers have beaten some of the greatest chess masters in the world. On IBM's website you have a dedicated page to the first complete match of 6 games lost by a chess master (Garry Kasparov) to a computer system (Deep Blue in this case). This happened in 1997. The competition between man and computers on this front is ongoing, with alternate victories on each side. More information on this wikipedia page.

So computers can successfully challenge the very best human chess players in the world. When you think that no computer system has succeeded in translating languages in a way that could challenge even an ordinary human translator's performance, you should start wondering. Language is way more complex than chess is, as complex as the human consciousness. Translation involves two different languages, each one with its own intricate structure and unique characteristics, so it requires as much highly skilled human intervention as possible.